JP5353569B2 - Turbo machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase critical speed of a shaft system in a turbo machine including a shaft journaled by a bearing, a bolt projecting from one end of the shaft, overlapping a rotary shaft of the shaft, and an impeller fixed on one end side of the shaft by a nut fitted on the bolt. <P>SOLUTION: In the turbo machine, an abutting surface 2a of the nut 11 is formed inside of the impeller 2, and the nut 11 is disposed inside of the impeller 2. The nut is disposed in a direction separating from the bearing further than the maximum outer diameter section of the impeller. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a turbomachine including an impeller fixed to one end of a shaft by a bolt and a nut.

  For example, in a turbo machine such as a turbo blower or a turbocharger, an impeller is fixed to at least one end side of a shaft pivotally supported by a bearing. Then, rotational power is supplied to the impeller through the shaft, and the impeller is rotationally driven.

In such a turbo machine, the shaft and the impeller are fastened by bolts and nuts.
Specifically, as shown in Patent Documents 1 to 3, a bolt that is projected from one end of the shaft so as to overlap the rotation shaft of the shaft is installed, and the tip of the bolt is passed through the center of the impeller. The impeller is fixed by exposing and fitting a nut to the exposed tip of the bolt.

JP-A-7-154010 JP-A-9-275234 JP 2006-214341 A

By the way, the impeller is fixed to a tip protruding far away from a portion supported by the shaft bearing. That is, the impeller is supported by a cantilever (so-called overhang). Furthermore, the impeller is very large with respect to the diameter of the shaft.
Since it has such an unstable shape, the critical speed in rotation of a shaft system such as a shaft or an impeller is reduced.

  In order to realize stable driving, ideally, a design in which the entire speed range up to the rated speed of the shaft system does not straddle the dangerous speed is preferable. However, at present, no method has been proposed to sufficiently increase the critical speed. Actually, the primary and secondary critical speeds are reduced after the spring stiffness of the bearing is lowered to suppress the shaft deflection. Is designed to straddle.

  The present invention has been made in view of the above-described problems, and is fitted to a shaft that is pivotally supported by a bearing, a bolt that protrudes from one end of the shaft so as to overlap the rotating shaft of the shaft, and the bolt. An object of the present invention is to increase the critical speed of a shaft system in a turbo machine including an impeller fixed to one end of the shaft by a nut.

  The present invention adopts the following configuration as means for solving the above-described problems.

  The first invention is fixed to one end of the shaft by a shaft supported by a bearing, a bolt protruding from one end of the shaft so as to overlap the rotating shaft of the shaft, and a nut fitted to the bolt. A configuration is adopted in which a contact surface of a nut is formed inside the impeller, and the nut is disposed inside the impeller.

  According to a second invention, in the first invention, a configuration is adopted in which the nut is disposed in a direction away from the bearing from a maximum outer diameter portion of the impeller in the rotation axis direction.

  According to a third invention, in the first or second invention, a configuration is adopted in which a tip of the bolt on the nut side is positioned inside the impeller.

  According to a fourth invention, in any one of the first to third inventions, a configuration is adopted in which an installation surface of the bolt in the shaft is disposed closer to the bearing than a maximum outer diameter portion of the impeller. .

  According to a fifth invention, in any one of the first to fourth inventions, a configuration is adopted in which the bolt is a tension bolt.

  In a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, a configuration in which an impeller structure that positions the impeller with respect to the shaft is employed.

According to the present invention, a nut that has been conventionally arranged outside the impeller is arranged inside the impeller. As a result, the center of gravity of the structure fixed to the one end side of the shaft approaches the bearing side, and the critical speed of the shaft system increases.
Therefore, according to the present invention, the shaft is supported by one end of the shaft by the shaft supported by the bearing, the bolt projecting from the one end of the shaft over the rotation shaft of the shaft, and the nut fitted to the bolt. In a turbo machine including a fixed impeller, the critical speed of the shaft system can be increased.

It is sectional drawing which shows schematic structure of the turbo blower in one Embodiment of this invention. It is an expanded sectional view showing a schematic structure of a turbo blower in one embodiment of the present invention. It is a perspective view which shows the jig | tool which tightens the nut used with the turbo blower in one Embodiment of this invention, and the said nut. It is drawing for demonstrating the effect of the turbo blower in one Embodiment of this invention. It is drawing which shows the change of a detuning rate at the time of changing a structure.

Hereinafter, an embodiment of a turbomachine according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.
In the following description, a turbo blower will be described as an example of the turbo machine of the present invention.

FIG. 1 is a cross-sectional view showing a schematic configuration of a turbo blower S1 of the present embodiment. The turbo blower S1 of this embodiment includes an impeller and a motor that directly drives the impeller to rotate, and pumps gas (fluid) by driving the motor.
As shown in FIG. 1, the turbo blower S1 of this embodiment includes a casing 1, an impeller 2, a motor 3, a shaft 4, a bearing 5, a hermetic connector 6, and a water cooling jacket 7. .

The casing 1 forms the outer shape of the turbo blower S1, and accommodates the gas flow path, the impeller 2, the motor 3, the shaft 4, the bearing 5, and the like therein.
As shown in FIG. 1, an impeller housing space K <b> 1 for housing the impeller 2 and a motor housing space K <b> 2 for housing the motor 3 are provided inside the casing 1. The casing 1 also includes a scroll flow path 1b that gently expands to a suction port 1a for sucking gas and a discharge port for discharging gas. The impeller accommodating space K1 is disposed between the suction port 1a and the scroll flow path 1b and is a part of the gas flow path.

  The impeller 2 is housed and disposed in the impeller housing space K1, and rotates to feed the gas supplied from the suction port 1a to the scroll passage 1b.

The motor 3 rotates the impeller 2 and is accommodated in the motor accommodating space K2. In the present embodiment, an induction motor is used as the motor 3.
The motor 3 includes a motor rotor 3a in which a cage-type conductive material (coil) is incorporated, and a motor stator 3b disposed so as to surround the motor rotor 3a. The motor rotor 3a rotates when electric power is supplied to the motor stator 3b from a drive device (not shown).

  The shaft 4 connects the motor 3 and the impeller 2, and transmits the power of the motor 3 to the impeller 2. More specifically, as shown in FIG. 1, the shaft 4 is inserted into the motor rotor 3 a with one end side fixed to the impeller 2, and rotates with the rotation of the motor rotor 3 a, thereby driving the power of the motor 3 to the impeller 2. To communicate.

The bearing 5 supports the shaft 4 in an upright state, and an inner ring is fixed to the shaft 4 and an outer ring is fixed to the casing 1.
As shown in FIG. 1, as the bearing 5, an impeller side bearing 5 a that supports the shaft 4 near the impeller 2 and a ground side bearing 5 b that supports the shaft 4 near the ground are provided. The ground-side bearing 5 b is slidable with respect to the casing 1 and is urged upward by a preload spring 8. Thus, the ground side bearing 5b is urged by the preload spring 8, so that the bearing is optimally preloaded, and the behavior of the balls inside the bearing 5 (5a, 5b) can be maintained in an appropriate state during rotation.

The hermetic connector 6 is a connector that enables power supply to the motor 3 while maintaining the state where the impeller accommodating space K1 and the motor accommodating space K2 are completely sealed, and is fixed to the casing 1 while being exposed to the outside. Yes.
Note that the turbo blower S1 of the present embodiment is mounted on a laser oscillation device and is assumed to pump gas in an environment where inflow of outside air is not permitted. For this reason, the hermetic connector 6 is used. However, when it is not necessary to completely seal the impeller accommodating space K1 and the motor accommodating space K2, a normal connector can be used instead of the hermetic connector 6.

  The water cooling jacket 7 is provided in the casing 1 around the motor 3 and cools the motor with cooling water.

  Here, in the turbo blower S1 of the present embodiment, as shown in the enlarged view of FIG. 2, a bolt 10 protruding from one end of the shaft 4 so as to overlap the rotation axis L of the shaft 4 is fitted to the bolt 10. The impeller 2 is fixed to one end side of the shaft 4 by the nut 11.

As shown in FIG. 2, in the turbo blower S <b> 1 of the present embodiment, the contact surface 2 a of the nut 11 formed on the impeller 2 is disposed inside the impeller 2. More specifically, a cylindrical opening 12 that is slightly larger than the outer shape of the nut 11 is formed from the top 2d of the impeller 2 toward the inside of the impeller 2, and this bottom surface serves as the contact surface 2a.
The nut 11 is fitted to the bolt 10 while being in contact with the contact surface 2a. For this reason, in the turbo blower S <b> 1 of the present embodiment, the nut 11 is arranged inside the impeller 2.

Further, the contact surface 2 a is disposed in a direction away from the bearing 5 than the maximum outer diameter portion 2 b of the impeller 2.
As a result, in the turbo blower S1 of the present embodiment, the nut 11 is disposed in a direction away from the bearing 5 rather than the maximum outer diameter portion 2b of the impeller 2.
The maximum outer diameter portion 2b of the impeller 2 is a portion in the rotation axis direction including the outermost periphery when the impeller 2 is viewed from the rotation axis direction except for the blades.

A through hole 13 having a diameter smaller than that of the opening 12 is formed in the bottom surface of the opening 12 so as to pass through the bottom of the impeller 2, and the bolt 10 is connected to the impeller from one end of the shaft 4 through the through hole 13. 2 is inserted inside. A tip 10 a on the nut 11 side of the bolt 10 is disposed inside the impeller 2.
In the turbo blower S <b> 1 of the present embodiment, tension bolts are used as the bolts 10.

Further, in the turbo blower S <b> 1 of the present embodiment, the installation surface 4 a of the bolt 10 in the shaft 4 is disposed closer to the bearing 5 than the maximum outer diameter portion 2 b of the impeller 2.
Furthermore, in the turbo blower S1 of the present embodiment, one end 4b of the shaft 4 including the installation surface 4a has a smaller diameter than the other parts of the shaft 4, and further, the end of the impeller 2 has the one end A hole 2c into which the portion 4b can be fitted is formed. The hole 2 c opens on the back surface (surface on the motor 3 side) of the impeller 2 and communicates with the through hole 13. Further, the inner diameter of the hole 2 c is set larger than the inner diameter of the through hole 13.
The installation surface 4a is an end surface of the shaft 4 (one end portion 4b), is substantially perpendicular to the central axis (rotation axis L) of the shaft 4, and is substantially circular when viewed from the central axis direction.

  Then, the impeller 2 is positioned with respect to the shaft 4 by fitting one end portion 4b of the shaft 4 into the hole 2c. That is, the turbo blower S <b> 1 of the present embodiment is configured by one end 4 b of the shaft 4 and a hole 2 c formed in the bottom of the impeller 2, and has an inlay structure 14 that positions the impeller 2 with respect to the shaft 4.

  The peripheral edge of the installation surface 4a is in contact with the bottom surface of the hole 2c (the inner surface on the bolt 10 side). The impeller 2 is fixed to the shaft 4 in the axial direction by sandwiching a portion where the through-hole 13 is formed from both sides by the installation surface 4 a and the nut 11.

  Further, as described above, the nut 11 is fitted to the bolt 10 at the bottom of the cylindrical opening 12 that is slightly larger than the outer shape of the nut 11, so that it is difficult to tighten with a normal hex wrench or the like. Therefore, in the turbo blower S1 of the present embodiment, as shown in FIG. 3, a plurality of holes 11a opened upward are formed in the upper portion of the nut 11, and the protruding portions 20a that can be inserted into the holes 11a. The nut 11 is tightened by using a dedicated jig 20 provided with.

The turbo blower S1 of the present embodiment configured as described above is driven by supplying electric power from a driving device (not shown) via the hermetic connector 6.
More specifically, the motor 3 is rotated by the drive signal, and the rotational power is transmitted to the impeller 2 through the shaft 4, so that the impeller 2 is rotationally driven.
As a result, gas is sucked into the impeller accommodating space K1 from the suction port 1a, and the gas is pumped to the scroll flow path 1b side by the impeller 2 that is rotationally driven.

  Here, in the turbo blower S <b> 1 of the present embodiment, a nut that is conventionally arranged outside the impeller 2 is arranged inside the impeller 2. As a result, the center of gravity of the structure fixed to one end side of the shaft 4 is shifted to the bearing 5 side, and the critical speed of the shaft system (the rotating system including the shaft 4 and the impeller 2) can be increased.

FIG. 4 is a diagram for comparing the critical speed of the shaft system in the conventional turbo blower in which the nut is arranged outside the impeller 2 and the critical speed of the shaft system in the turbo blower S1 of the present embodiment. In FIG. 4, the horizontal axis indicates the spring constant (rigidity) of the bearing 5, and the vertical axis indicates the critical speed.
In FIG. 4, Mode 1 indicated by a solid line indicates the primary dangerous speed in the turbo blower S1 of the present embodiment, Mode 2 indicated by a solid line indicates the secondary dangerous speed in the turbo blower S1 of the present embodiment, and Mode 3 indicated by a solid line is the main speed. The third critical speed in the turbo blower S1 of the embodiment is shown, Mode 4 shown by a solid line shows the fourth critical speed in the turbo blower S1 of the present embodiment, Mode 1 shown by a broken line shows the primary dangerous speed in the conventional turbo blower, and the broken line Mode 2 shown indicates the secondary critical speed in the conventional turbo blower, Mode 3 indicated by the broken line indicates the tertiary critical speed in the conventional turbo blower, and Mode 4 indicated by the broken line indicates the fourth critical speed in the conventional turbo blower.

And as shown in FIG. 4, it turns out that the turbo blower S1 of this embodiment has raised all the 1st-4th critical speeds compared with the conventional turbo blower.
The spring constant of the bearing 5 in the turbo blower S1 of this embodiment is 2. E + 05. In terms of this spring constant, in the turbo blower S1 of the present embodiment, the entire speed range up to a 25% increase in the rated speed and further the rated speed does not straddle the dangerous speed. Therefore, the turbo blower S1 of the present embodiment can be driven stably.
Further, as shown in FIG. 4, if the spring constant of the bearing 5 is 1. Even in the case of E + 05, the dangerous speed is not crossed over the entire speed range up to the rated speed. For this reason, according to the turbo blower S1 of the present embodiment, it can be employed even when the spring constant of the bearing 5 is small.

Note that the inside of the maximum outer diameter portion 2b of the impeller 2 is a region where the stress caused by the centrifugal force acts most. On the other hand, in the turbo blower S1 of the present embodiment, since the opening 12 is larger than the outer shape of the nut 11, there is a possibility that the internal hollow region becomes wide and local stress concentration becomes large.
In contrast, in the turbo blower S1 of the present embodiment, the nut 11 is disposed in a direction away from the bearing 5 rather than the maximum outer diameter portion 2b of the impeller 2. For this reason, the internal thickness of the maximum outer diameter portion 2b of the impeller 2 can be ensured similarly to the conventional turbo blower, and the stress that the impeller 2 can withstand can be ensured to the same extent as the conventional turbo blower.

  In the turbo blower S <b> 1 of the present embodiment, a tension bolt is used as the bolt 10. For this reason, even if the impeller 2 is a case where the length of a rotating shaft direction becomes short with centrifugal force, the impeller 2 can be reliably fixed with respect to the shaft 4.

  Further, the turbo blower S1 of the present embodiment has an inlay structure 14 that is configured by one end portion 4b of the shaft 4 and a hole 2c formed in the bottom portion of the impeller 2, and that positions the impeller 2 with respect to the shaft 4. . For this reason, positioning with the shaft 4 and the impeller 2 can be performed easily and reliably.

FIG. 5 shows how the detuning rate between the rated operation and the primary critical speed changes by changing the configuration while keeping the spring constant of the bearing constant (2.E + 05). FIG.
In FIG. 5, the horizontal axis indicates the fastening position on the bearing side (that is, the position of the installation surface 4a of the bolt 10), and the vertical axis indicates the detuning rate between the rated operation and the primary dangerous speed.

Points A to H are views showing the result of moving the installation surface 4a in a state where the nut 11 is arranged outside the impeller 2 as shown in FIG.
As can be seen from these points A to H, it can be seen that the detuning rate increases, that is, the critical speed increases as the installation surface 4a approaches the bearing 5 side. Further, when the installation surface 4a is located closer to the bearing 5 than the maximum outer diameter portion 2b (point G and point H), the detuning rate can be reliably increased.
And in turbo blower S1 of this embodiment, since the structure where the installation surface 4a is located near the bearing 5 rather than the largest outer-diameter part 2b is employ | adopted, a dangerous speed can be raised reliably.

Further, as can be seen from the point I, it can be seen that by arranging the nut 11 inside the impeller 2 as shown in (b), the detuning rate is significantly increased, that is, the critical speed is significantly increased.
Further, as can be seen from the point J, as shown in (c), it can be seen that by arranging the tip 10a of the bolt 10 inside the impeller 2, the detuning rate further increases, that is, the critical speed further increases. . The point J is the result of the turbo blower S1 of the present embodiment.
Point K shows the result of placing the installation surface 4 a closer to the bearing 5 in a state where the nut 11 and the tip 10 a of the bolt 10 are arranged inside the impeller 2. As can be seen from the relationship between the point J and the point K and the relationship between the point G and the point H, even if the nut 11 and the tip 10a of the bolt 10 are disposed inside the impeller 2, the nut 11 It can be seen that the detuning rate changes similarly to the configuration of (a) arranged outside.
Point L and point M show the result when the protrusion amount d of the bottom of the impeller 2 is changed as shown in (d). When the point L is originally 10 mm and the protrusion amount is 8 mm, the point M is originally This is the result when the protruding amount of 10 mm is 6 mm. When obtaining this result, the position of the bearing 5 was also changed as shown in FIG. As can be seen from the points L and M, it can be seen that the detuning rate increases, that is, the critical speed increases by reducing the protrusion amount d. However, the protrusion at the bottom of the impeller 2 is originally formed to increase the stress that the impeller can withstand. For this reason, it is necessary to set the protrusion amount d at the bottom of the impeller 2 in consideration of the balance between the impeller rigidity and the critical speed.

  As mentioned above, although preferred embodiment of this invention was described referring drawings, this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

For example, in the above embodiment, the configuration in which the turbo machine of the present invention is a turbo blower has been described.
However, the present invention is not limited to this, and for example, a turbo pump or the like can be used as the turbo machine of the present invention.

  S1 ... Turbo blower (turbo machine), 2 ... impeller, 2a ... contact surface, 2b ... maximum outer diameter part, 4 ... shaft, 4a ... installation surface, 5 ... bearing, 10 ... bolt, 10a …… Tip, 11 …… Nut, 14 …… Inlay structure

Claims (1)

A turbo comprising: a shaft supported by a bearing; a bolt protruding from one end of the shaft so as to overlap the rotating shaft of the shaft; and an impeller fixed to one end of the shaft by a nut fitted to the bolt A machine,
A contact surface of a nut is formed inside the impeller, and the whole of the nut is disposed inside the impeller .
In the rotational axis direction, the nut is disposed in a direction away from the bearing than the maximum outer diameter portion of the impeller,
The nut-side tip of the bolt is located inside the impeller,
The installation surface of the bolt in the shaft is disposed closer to the bearing than the maximum outer diameter portion of the impeller,
The bolt is a tension bolt;
A turbomachine having an inlay structure for positioning the impeller with respect to the shaft .

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